1. Field of the Invention
This invention relates to a photometric device for obtaining a photometric value by dividing a photographing field into a plurality of photometric areas and by computing in varied manners information on measured luminance of each of the areas.
2. Description of the Related Art
There have been proposed various photometric devices of the kind arranged to divide a photographing field into a plurality of areas, to obtain a plurality of measured light values by measuring the light of each of the areas and to give a suitable exposure to a photo taking image plane on the basis of the measured values.
For example, Japanese Utility Model Publication No. SHO 51-9271 has disclosed a photometric device which obtains an apposite photometric value by using an arithmetical mean of the maximum and minimum values of the photo-electic outputs of a plurality of photo-electric elements. This photometric device, however, has presented a problem that an under- or over-exposure results from such a photographing object that has an unusually bright or dark background. Further, U.S. Pat. No. 4,476,383 discloses a photometric device which is arranged such that, in case where, some of the outputs of a plurality of photo-electric elements comes to exceed a given threshold value for a number of times exceeding a given number of times, a computing operation is performed by replacing the exceeding portion of the outputs with a predetermined value. This device is, however, arranged to give a predetermined exposure even in cases where it is inadequate, because any object luminance level that exceeds a given luminance value is undeterminable. For example, in photographing a white object under a clear sky, the exposure becomes either an over-exposure or an under-exposure according to the intensity of light on the object. It is another problem with this device that, since accurate luminance difference information is not obtainable at a luminance level around the given threshold value, it is impossible to determine an exposure by judging the lightness or luminance distribution of the photographing field. U.S. Pat. No. 4,561,753 also has made a disclosure on a concept similar to that of the above cited U.S. Pat. No. 4,476,383.
Further, although it cannot be regarded, in the strict sense, as the prior art relative to this invention, the present inventor has previously invented photometric devices of the kind arranged to divide a photographing field into a plurality of photometric areas to measure the light of each of these areas and to obtain a photometric value by computing information on a plurality of luminance values obtained from these areas. These devices are disclosed respectively in U.S. Pat. application Ser. Nos. 894,613 filed Aug. 8, 1986, 009,995 filed Feb. 2, 1987, and 043,935 filed Apr. 29, 1987.